[BUG] gpu: drm: amd: amdgpu: possible ABBA deadlock in amdgpu_set_power_dpm_force_performance_level() and amdgpu_debugfs_process_reg_op()

[Jia-Ju Bai]

Hello,

My static analysis tool reports a possible ABBA deadlock in the amdgpu 
driver in Linux 5.10:

amdgpu_debugfs_process_reg_op()
  mutex_lock(&adev->grbm_idx_mutex); --> Line 250 (Lock A)
  mutex_lock(&adev->pm.mutex); --> Line 259 (Lock B)

amdgpu_set_power_dpm_force_performance_level()
  mutex_lock(&adev->pm.mutex); --> Line 381 (Lock B)
    pp_dpm_force_performance_level() --> function pointer via 
"amdgpu_dpm_force_performance_level()"
      pp_dpm_en_umd_pstate()
        amdgpu_device_ip_set_clockgating_state()
          gfx_v7_0_set_clockgating_state() --> function pointer via 
"funcs->set_clockgating_state()"
            gfx_v7_0_enable_mgcg()
              mutex_lock(&adev->grbm_idx_mutex); --> Line 3646 (Lock A)
              mutex_lock(&adev->grbm_idx_mutex); --> Line 3697 (Lock A)

When amdgpu_debugfs_process_reg_op() and 
amdgpu_set_power_dpm_force_performance_level() are concurrently 
executed, the deadlock can occur.

I am not quite sure whether this possible deadlock is real and how to 
fix it if it is real.
Any feedback would be appreciated, thanks :)

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>


Best wishes,
Jia-Ju Bai